Posted at the same time, check your attitude during ATT alignment, it must be leveled in pitch and roll.Or problems occurs.I had no code 3 error, I'll check what it mean.Code 3 is excessive motion, you probably switched to nav position for seconds before putting on ATT, so IRS accelerometers detects that aircraft is moving, when it is supposed to be on ground, moving on ATT I tink must extinguish the fault code 3 as no accelerometers are used.

Yes,code 03 is not stable level flight with ATT.And i notice if get code 03,turn to OFF wait ALIGN extinguish,then turn to ATT and flight stable, wait few sec SET IRS HDG will appear on fmc(code 09),set it then AP function get back.I will practice more time,because i was happened ac transfer bus failure before.then i manual remainder of flight,it's terrible experience.Thanks Andrea.

Took me a good time of testing and waiting (level flight) but at last this did work. Need to use 'no weater' so that I could better keep level flight.One little correction. Entering the irs hdg (mag) needs to be done at POS INIT page 5R.Maikel Rozemeijer